Up to today scientists have described about 270,000 species of mosses, ferns, conifers and flowering plants (Angiosperms), but it is believed that there are more than 30.000 species still unknown, especially in the luxuriant tropical forests.

Plant biodiversity is perhaps man’s greatest natural resource from of old. From a reduced number of forest plants, man has selected and developed hundreds of thousands of varieties which, even at present, constitute our greatest resource of subsistence. During the 20th century farmers have used this genetic heritage for creating very productive crops, and scientists have also created modified seeds, from a genetic point of view, to obtain a still more attractive quality for the consumer. The productivity of our agriculture is, however, linked to the variety of wild species in nature and, as a matter of fact, we have to draw on this “source” of genes to replace the loss of variability which is the product of highly selected cultivated species. Extends of graminaceas

Extends of graminaceas (© 2005 G. Farano) Wheat cultivated field (© 2005 P. Pavone - DBUC).

A useful example in this sense is the wild potato. These insignificant, weak plants, with small underground tubercles, have been found to be indispensable for fighting against mildew (Phytophthora infestans). Between 1835 and 1840 this fungus destroyed all the crops in Europe, resulting in a shortage that, in Ireland alone, killed about 2 million persons. This disease was controlled by fungicides in the course of the last century, but around the mid-eighties, farmers found signs of mildew “resistant” forms. These forms, particularly virulent, reduced during the nineties the global production of potatoes by a 15%, with the consequent economic loss of 3.25 billions dollars. In some regions, like the high plateaus of Tanzania, losses induced by Phytophtora were close to 100%. Luckily, scientists of the International Center of Potatoes, Lima (Peru) realised that the traditional crops of the Andes, the same as the wild species, were resistant to the mildew. The hybridisation between resistant species and cultivated potatoes in Europe introduced the gene of the resistant element, solving the problem.

The potato, native of the Andes, was cultivated by the Indios in Peru some 5000 years ago

But plants are not only a source of nutrition and genes for man, they are also necessary to maintain good health and to improve the quality of life. A great number of remedies which nowadays cure illnesses possess chemical substances of vegetal origin. But medicinal plants are also rare in nature because of the destruction of forests and alterations to ecosystems that will lead not only to the loss of biodiversity, but also to the disappearance of active principles and remedies for the future.

In some places were life conditions are precarious, plants not only provide food and medicine but also refuge, tools and fire
(© 2005 Martino Coppola di Canzano)